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Analysis and Design of Transmission Tower

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Electrical Engineering,Mechanical Engineering,Computer Science & Engineering,Artificial Intelligence,Material Science,Mathematicse,Applied physics,Applied Chemistry,Electronics …

Electrical Engineering,Mechanical Engineering,Computer Science & Engineering,Artificial Intelligence,Material Science,Mathematicse,Applied physics,Applied Chemistry,Electronics Engineering,Instrumentation Engineering,Civil Engineering,Earth quake Engineering,Structural engineering,

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  • 1. International OPEN Journal ACCESS Of Modern Engineering Research (IJMER) Analysis and Design of Transmission Tower Gopi Sudam Punse ABSTRACT: In this thesis Analysis and Design of narrow based Transmission Tower (using Multi Voltage Multi Circuit) is carried out keeping in view to supply optimum utilization of electric supply with available ROW and increasing population in the locality, in India. Transmission Line Towers constitute about 28 to 42 percent of the total cost of the Transmission Lines. The increasing demand for electrical energy can be met more economical by developing different light weight configurations of transmission line towers. In this project, an attempt has been made to make the transmission line more cost effective keeping in view to provide optimum electric supply for the required area by considering unique transmission line tower structure. The objective of this research is met by choosing a 220KV and 110KV Multi Voltage Multi Circuit with narrow based Self Supporting Lattice Towers with a view to optimize the existing geometry. Using STAAD PRO v8i analysis and design of tower has been carried out as a three dimensional structure. Then, the tower members are designed. I. INTRODUCTION 1.1 Transmission Line Tower India has a large population residing all over the country and the electricity supply need of this population creates requirement of a large transmission and distribution system. Also, the disposition of the primary resources for electrical power generation viz., coal, hydro potential is quite uneven, thus again adding to the transmission requirements. Transmission line is an integrated system consisting of conductor subsystem, ground wire subsystem and one subsystem for each category of support structure. Mechanical supports of transmission line represent a significant portion of the cost of the line and they play an important role in the reliable power transmission. They are designed and constructed in wide variety of shapes, types, sizes, configurations and materials. The supporting structure types used in transmission lines generally fall into one of the three categories: lattice, pole and guyed. The supports of EHV transmission lines are normally steel lattice towers. The cost of towers constitutes about quarter to half of the cost of transmission line and hence optimum tower design will bring in substantial savings. The selection of an optimum outline together with right type of bracing system contributes to a large extent in developing an economical design of transmission line tower. The height of tower is fixed by the user and the structural designer has the task of designing the general configuration and member and joint details. The goal of every designer is to design the best (optimum) systems. But, because of the practical restrictions this has been achieved through intuition, experience and repeated trials, a process that has worked well. Power Grid Corporations of India Limited has prescribed the following steps to. Optimized the Design of Power Transmission Lines: o Selection of clearances. o Insulator and insulator string design. o Bundle conductor studies. o Tower configuration analysis. o Tower weight estimation. o Line cost analysis and span optimization. o Economic evaluation of line. | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |116|
  • 2. Analysis and Design of Transmission Tower Figure 1.1 Transmission line tower 1.2 LITERATURE REVIEW Research paper 1.2.1 Y. M. Ghugal , U. S. Salunkhe [1] “Analysis and Design of Three and Four Legged 400KV Steel Transmission Line Towers: Comparative Study” H.O.D. Applied Mechanics Department, Govt. College of Engineering, Aurangabad Maharashtra (India), Post Graduate Student of M.E. (Structural Engineering), Applied Mechanics Department, Govt. College of Engineering, Aurangabad. International Journal of Earth Sciences and Engineering 691 ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp 691-694 Abstract: The four legged lattice towers are most commonly used as transmission line towers. Three legged towers only used as telecommunication, microwaves, radio and guyed towers but not used in power sectors as transmission line towers. In this study an attempt is made that the three legged towers are designed as 400 KV double circuit transmission line tower. The present work describes the analysis and design of two selfsupporting 400 KV steel transmission line towers viz three legged and four legged models using common parameters such as constant height, bracing system, with an angle sections system are carried out. In this study constant loading parameters including wind forces as per IS: 802 (1995) are taken into account. After analysis, the comparative study is presented with respective to slenderness effect, critical sections, forces and deflections of both three legged and four legged towers. A saving in steel weight up to 21.2% resulted when a three legged tower is compared with a four legged type. 1.2.2 V. Lakshmi1, A. Rajagopala Rao [2] “EFFECT OF MEDIUM WIND INTENSITY ON 21M 132kV TRANSMISSION TOWER” Assistant Professor, Civil Engineering, JNT University Kakinada, Andhra Pradesh, India, Professor of Civil Engineering (Retd) JNT University Kakinada, Andhra Pradesh, India, ISSN: 2250–3676 Volume-2, Issue-4, 820 – 824 Abstract: In this paper the performance of 21M high 132kV tower with medium wind intensity is observed. The Recommendations of IS 875-1987, Basic wind speeds, Influence of height above ground and terrain, Design wind speed, Design wind pressure, Design wind force is explained in detailed. An analysis is carried out for the tower and the performance of the tower and the member forces in all the vertical, horizontal and diagonal members are evaluated. The critical elements among each of three groups are identified. In subsequent chapters the performance of tower under abnormal conditions such as localized failures are evaluated. The details of load calculation, modeling and analysis are discussed. The wind intensity converted into point loads and loads are applied at panel joints. 1.2.3 M.Selvaraj, S.M.Kulkarni, R.Ramesh Babu [3] “Behavioural Analysis of built up transmission line tower from FRP pultruded sections” Central Power Research Institute, Bangalore, India , National Institute of Technology Karnataka, Mangalore, India ISSN 2250-2459, Volume 2, Issue 9, September 2012 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |117|
  • 3. Analysis and Design of Transmission Tower Abstract: The power transmission line towers will have to be built with new design concepts using new materials, reduction of construction costs and optimizing power of delivery with restricted right of way. This paper discusses experimental studies carried out on a X-braced panel of transmission line tower made from FRP pultruded sections. Mathematical model of individual members and members in the X-braced panel are generated using FEM software to study the analytical correlation with the experiments. The member stresses are monitored using strain gauges during full scale testing. Conclusions are drawn based on these studies. 1.2.4 S.Christian Johnson 1 G.S.Thirugnanam [4] Research Scholar, Head & Professor in civil Engg. IRTT “Experimental study on transmission line tower foundation and its rehabilitation” International Journal of Civil Engineering ISSN 0976 – 4399 Volume 1, No 1, 2010 corrosion of and Structural Abstract: In transmission line towers, the tower legs are usually set in concrete which generally provides good protection to the steel. However defects and cracks in the concrete can allow water and salts to penetrate with subsequent corrosion and weakening of the leg. When ferrous materials oxidized to ferrous oxide (corrosion) its volume is obviously more than original ferrous material hence the chimney concrete will undergo strain resulting in formation of cracks. The cracks open, draining the water in to chimney concrete enhancing the corrosion process resulting finally in spelling of chimney concrete. This form of corrosion of stub angle just above the muffing or within the muffing is very common in saline areas. If this is not attended at proper time, the tower may collapse under abnormal climatic conditions. Maintenance and refurbishment of in-service electric power transmission lines require accurate knowledge of components condition in order to develop cost effective programs to extend their useful life. Degradation of foundation concrete can be best assessed by excavation. This is the most rigorous method since it allows determination of the extent and type of corrosion attack, including possible involvement of microbial induced corrosion. In this paper, Physical, Chemicaland electro chemical parameters, studied on transmission line tower stubs excavated from inland and coastal areas have been presented. A methodology for rehabilitation of transmission tower stubs has been discussed. 1.2.5 F.Albermani and M. Mahendran [5] “Upgrading Of Transmission Towers Using Of Diaphragm Bracing System” Dept. of Civil Engineering, University of Queensland, Brisbane, Australia School of Civil Engineering, Queensland University of Technology, Brisbane, Australia Dept. of Building and Construction, City University of Hong Kong, Hong Kong . Abstract: Many older transmission towers are designed based on tension-only bracing systems with slender diagonal members. However, the increased demand in power supply and changing global weather patterns mean that these towers require upgrading to carry the resultant heavier loading. The failure of a single tower can rapidly propagate along the line and result in severe damage that costs many millions of dollars. Hence, this research project is aimed at developing efficient upgrading schemes using diaphragm bracings. Tower strength improvement was investigated by adding a series of diaphragm bracing types at mid-height of the slender diagonal members. Analytical studies showed that considerable strength improvements could be achieved using diaphragm bracings. They also showed the effects of different types of bracings, including those of joining the internal nodes of diaphragm members and the location of diaphragms. Experimental studies were undertaken using a tower sub-structure assembly that was strengthened with a variety of diaphragm bracings under two types of loading. The results confirmed the analytical predictions and allow recommendations on the most efficient diaphragm bracing types. This type of upgrading scheme using the most efficient diaphragm bracing type was successfully implemented on an existing 105 m height TV tower. This paper presents the details of both the analytical and experimental studies and their results. 1.2.6 N.PrasadRao, G.M.Samuel Knight, S.J.Mohan, N. Lakshmanan [6] “Studies on failure of transmission line towers in testing” College of Engineering Gunidy ,Anna University, Chennai 600 025 India, Structural Engineering Research Center, Chennai 600 113,India Abstract: The towers are vital components of the transmission lines and hence, accurate prediction of their failure is very important for the reliability and safety of the transmission system. When failure occurs, direct and indirect losses are high, leaving aside other costs associated with power disruption and litigation. Different | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |118|
  • 4. Analysis and Design of Transmission Tower types of premature failures observed during full scale testing of transmission line towers at Tower Testing and Research Station, Structural Engineering Research Centre, Chennai are presented. Failures that have been observed during testing are studied and the reasons discussed in detail. The effect of non-triangulated hip bracing pattern and isolated hip bracings connected to elevation redundant in „K‟ and „X‟ braced panels on tower behaviour are studied. The tower members are modelled as beam column and plate elements. Different types of failures are modelled using finite element software and the analytical and the test results are compared with various codal provisions. The general purpose finite element analysis program NE-NASTRAN is used to model the elasto-plastic behaviour of towers. Importance of redundant member design and connection details in overall performance of the tower is discussed. 1.2.7 G.Visweswara Rao[7] “OPTIMUM DESIGNS FOR TRANSMISSION LINE TOWERS” Senior research Analyst, Engineering Mechanics Research India, 907 Barton Centre Bangalore-560 001, India Computer & Structures vol.57.No.1.pp.81-92, 1995 Abstract: A method for the development of optimized tower designs for extra high-voltage transmission lines is presented in the paper. The optimization is with reference toboth tower weight and geometry. It is achieved by the control of a chosen set of key design parameters. Fuzziness in the definition of these control variables is also included in the design process . A derivative free method of nonlinear optimization is incorporated in the program, specially developed for the configuration, analysis and design of transmission line towers. A few interesting result of both crisp and fuzzy optimization, relevant to the design of a typical double circuit transmission line tower under multiple loading condition, are presented. II. ANALYSIS OF TRANSMISSION LINE TOWER 2.1 Details of Electric Tension Tower 220kv over 110kv Wind Pressure Details:Basic wind speed Vb = 44 m/s Wind zone – 3 Reliability level – 2 Terrain category – 2 Reference wind speed = VR = Vb/Ko = 44/1.375 = 32m/s Design wind speed Vd= VR*K1*K2 K1= 1.11 K2= 1 Vd = 32*1.11*1 = 35.52m/s Design wind pressure Pd = 0.6*Vd2 = 0.6*35.522 = 757 N/m2 = 77.17Kg/m2 Max. Temperature of conductor = 750C Max. Temperature of earth wire = 530C Everyday temperature = 320C Min. temperature = 00C For 220KV : Conductor wire Total wind load on conductor = Cdc*Gc * Ae* Pd* space factor Cdc= 1 Gc = 2.32 Ae = 3.16x10-2x1 m2/m = 3.16x10-2 m2/m Space factor = 0.6 For 100% wind, Pd = 1*2.32*3.18 x10-2 *77.17*0.6 = 3.416 For 36% wind, Pd= 0.36* 1*2.32*3.18 x10-2 *77.17*0.6 = 1.25 For 75% wind, Pd= 0.75* 1*2.32*3.18 x10-2 *77.17*0.6 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |119|
  • 5. Analysis and Design of Transmission Tower = 2.562 W = 2.004 Q1 = BY parabola equation T2 (T- K + Αaet) = W2L2EA / 24Q2 T = UTS/FOS = 16438/4 = 4109.5 Initial cond. – at 320C & 0% wind 4109.52 (4109.5 – K + 1.93X10-5x5.97x10-4x7x109x32) = 2.0042x3202x7x109x5.97x10-4/24x12 K = 2450.326 Put K = 2450.326 in above equation, find out tension and sag in conductor as given in below mentioned table. Sag = W*L2/8T Ground wire Total wind load on conductor = Cdc* Gc * Ae* Pd* space factor Cdc= 1.2 Gc = 2.39 Ae = 9.45x10-3x1 m2/m = 9.45x10-3 m2/m Space factor =0.6333 For 100% wind, Pd = 1.2*2.39*9.45 x10-3 *77.17*0.6 = 1.255 For 36% wind, Pd= 0.36* 1.2*2.39*9.45 x10-3 *77.17*0.6 = 0.452 For 75% wind, Pd= 0.75* 1.2*2.39*9.45 x10-3 *77.17*0.6 = 0.941 W = 0.429 Q1 = …………as per IS 5613 By parabola equation T2 (T- K + Αaet) = W2L2EA / 24Q2 T = UTS/FOS = 5913/4 = 1478.25 Initial cond. – at 320C & 0% wind 1478.252 (1478.25– K + 1.15X10-5x5.46x10-5x1.93x1010x32) = 0.4292x3202x1.93x1010x5.46x10-5/24x12 K = 1487.374 Sag in ground wire at 0® C & 0% wind = 90% of sag in conductor 0® C & 0% wind = 0.9*4.981 = 4.48 Put K = 1487.374 in above equation, find out tension and sag in conductor. Sag = W*L2/8T For 110KV : Conductor wire Total wind load on conductor = Cdc*Gc * Ae* Pd* space factor Cdc= 1 Gc = 2.12 Ae = 2.1x10-2x1 m2/m = 2.1x10-2 m2/m Space factor =0.6 For 100% wind, Pd = 1*2.12*2.1 x10-2 *77.17*0.6 = 2.061 For 36% wind, Pd= 0.36* 1*2.12*2.1 x10-2 *77.17*0.6 = 0.742 For 75% wind, Pd= 0.75* 1*2.12*2.1 x10-2 *77.17*0.6 = 1.546 W = 0.974 Q1 = BY parabola equation T2 (T- K + Αaet) = W2L2EA / 24Q2 T = UTS/FOS =9144/4 = 2286 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |120|
  • 6. Analysis and Design of Transmission Tower Initial cond. – at 32®C & 0% wind 22862 (2286– K + 1.78X10-5x2.62x10-4x8.16x109x32) = 0.9422x3202x8.16x109x2.62x10-4/24x12 K = 1848 Put K = 1848 in above equation, find out tension and sag in conductor. Sag = W*L2/8T 2.2 GEOMETRY OF TOWER 1. Vertical spacing between conductors of 220KV = 5.5 m 2. Vertical spacing between top conductor and ground wire = 7.45 m 3. Vertical spacing between conductors of 110KV = 4.5m 4. Clearance between BC and TC1(including insulator string = 2.34m) = 7m 5. Ground clearance = 7.015m 6. Extra height at ground level = 3.665m 7. Max. sag = 7m 8. Height of Insulator string = 1.82 m Total height of tower = 1+2+3+4+5+6+7+8+9 = 53.95 m Cross arm length 220KV = 4.6m Cross arm length 110KV = 3.8m Base width 1/8*53.95 = 6.774 say 6m Width at waist level = ½*6 = 3m………..standard practice in use Inclination at base = 2.419 0 Please see the Excel sheet attached Figure 4.1 LOAD CASE 1:- Loads acting on transmission tower under normal (intact wire) Condition. Figure 4.2 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |121|
  • 7. Analysis and Design of Transmission Tower LOAD CASE 2:- Loads acting on transmission tower under broken wire condition. Figure 4.3 LOAD CASE 3:- Loads acting on transmission tower under broken wire condition 2.3 RESULT :Different Values of stresses obtained from STAAD - Pro V8i are as, OTHER DIAGONALS LEG MEMBER Axial Beam L/C N/mm2 BRACINGS Beam L/C Axial N/mm2 Beam L/C Axial N/mm2 57 1 -753.11 6 1 74.992 123 1 -0.004 58 1 -636.08 10 1 80.152 124 1 0.002 59 1 -497.34 14 1 87.46 125 1 -0.007 75 1 -753.12 33 1 0.157 126 1 0.001 76 1 -753.12 37 1 0.172 127 1 0.004 77 1 -636.09 63 1 -174 128 1 -0.004 78 1 -636.09 64 1 -199.8 129 1 0.002 79 1 -497.34 65 1 -233.7 130 1 -0.011 80 1 -497.34 69 1 -0.371 131 1 0.002 195 1 790.005 70 1 -0.44 132 1 0.004 196 1 672.947 71 1 -0.532 133 1 -0.001 197 1 534.176 87 1 -174 134 1 0 213 1 790.003 88 1 -174 135 1 -0.008 214 1 790.001 89 1 -199.8 136 1 0.003 215 1 672.945 90 1 -199.8 137 1 0.003 216 1 672.943 91 1 -233.7 153 1 -0.002 217 1 534.174 92 1 -233.7 154 1 0.001 218 1 534.175 99 1 -0.372 155 1 0.001 333 1 743.78 100 1 -0.371 156 1 -0.004 334 1 634.02 101 1 -0.439 157 1 0.001 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |122|
  • 8. Analysis and Design of Transmission Tower 335 1 504.169 102 1 -0.439 158 1 0.001 351 1 743.779 103 1 -0.53 159 1 -0.001 352 1 743.776 104 1 -0.53 160 1 -0.003 353 1 634.018 111 1 74.992 161 1 0.002 354 1 634.016 112 1 80.152 162 1 -0.001 355 1 504.167 113 1 87.46 163 1 0 356 1 504.168 117 1 0.157 164 1 -0.001 471 1 -706.89 118 1 0.172 165 1 -0.005 472 1 -597.15 183 1 -0.156 166 1 0.003 473 1 -467.32 184 1 -0.171 167 1 -0.001 489 1 -706.89 185 1 -44.57 261 1 -0.002 490 1 -706.9 189 1 -70.73 262 1 0.001 491 1 -597.15 190 1 -75.45 263 1 -0.001 492 1 -597.16 191 1 -80.22 264 1 0 493 1 -467.33 201 1 0.373 265 1 0.001 494 1 -467.34 202 1 0.442 266 1 -0.004 597 1 -149.32 203 1 0.533 267 1 0.003 598 1 -151.59 207 1 173.96 268 1 -0.002 599 1 179.969 208 1 199.8 269 1 -0.001 600 1 178.235 209 1 233.7 270 1 0.001 605 1 -115.43 225 1 0.373 271 1 -0.003 606 1 -79.894 226 1 0.373 272 1 0.002 607 1 -120.41 227 1 0.44 273 1 0.003 608 1 -81.925 228 1 0.441 274 1 -0.003 609 1 140.432 229 1 0.531 275 1 0.001 610 1 97.978 230 1 0.532 291 1 -0.005 611 1 133.504 237 1 173.96 292 1 0.001 612 1 98.873 238 1 173.96 293 1 0.004 681 1 -52.997 239 1 199.79 294 1 -0.001 682 1 -52.623 240 1 199.79 295 1 0 683 1 71.268 241 1 233.69 296 1 -0.013 684 1 70.752 242 1 233.7 297 1 0.001 689 1 -35.244 249 1 -0.156 298 1 0.004 690 1 -17.945 250 1 -0.171 299 1 -0.001 691 1 -38.693 251 1 -44.57 300 1 0.002 692 1 -17.607 255 1 -70.73 301 1 -0.005 693 1 49.069 256 1 -75.45 302 1 0.001 694 1 25.484 257 1 -80.22 303 1 0.006 695 1 43.915 321 1 -66.62 304 1 -0.003 696 1 27.322 322 1 -70.94 305 1 0.002 761 1 -9.418 323 1 -75.2 399 1 -0.009 762 1 -10.799 327 1 0.156 400 1 0.001 763 1 9.138 328 1 0.172 401 1 -0.001 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |123|
  • 9. Analysis and Design of Transmission Tower 764 1 17.29 329 1 -44.19 402 1 0 829 1 503.282 339 1 164.16 403 1 0.004 830 1 -469.84 340 1 188.19 404 1 -0.005 831 1 -441.06 341 1 219.71 405 1 0.001 832 1 474.501 345 1 -0.372 406 1 0.003 833 1 479.849 346 1 -0.439 407 1 -0.001 834 1 -432.89 347 1 -0.529 408 1 0.004 835 1 -406.82 363 1 164.16 409 1 -0.005 836 1 453.777 364 1 164.15 410 1 0.001 873 1 -364.02 365 1 188.19 411 1 0.005 874 1 421.143 366 1 188.19 412 1 -0.003 875 1 444.156 367 1 219.7 413 1 0.003 876 1 -387.04 368 1 219.71 429 1 -0.002 885 1 -351.47 375 1 -0.372 430 1 0.001 886 1 397.237 376 1 -0.371 431 1 0.001 887 1 377.707 377 1 -0.441 432 1 -0.001 888 1 -331.94 378 1 -0.44 433 1 0 1022 1 -193.48 379 1 -0.531 434 1 -0.004 1023 1 231.775 380 1 -0.53 435 1 0.003 1024 1 234.981 387 1 -66.62 436 1 -0.002 1025 1 -196.68 388 1 -70.94 437 1 -0.001 1030 1 -240.57 389 1 -75.2 438 1 -0.001 1031 1 -291.69 393 1 0.156 439 1 -0.003 1032 1 287.108 394 1 0.172 440 1 0.002 1033 1 332.089 395 1 -44.19 441 1 0.003 1034 1 296.506 459 1 -0.155 442 1 -0.003 1035 1 347.075 460 1 -0.171 443 1 -0.001 1036 1 -249.97 465 1 70.887 537 1 -0.002 1037 1 -306.68 466 1 75.633 538 1 0.001 1304 1 5.326 467 1 82.441 539 1 -0.004 1305 1 -2.028 477 1 0.373 540 1 0.001 1306 1 6.126 478 1 0.441 541 1 0.001 1307 1 1.319 479 1 0.53 542 1 -0.001 1308 1 -10.738 483 1 -164.2 543 1 0 1309 1 -5.346 484 1 -188.2 544 1 -0.006 1310 1 11.164 485 1 -219.7 545 1 0.002 1311 1 5.767 501 1 0.372 546 1 0.001 1328 1 -5.347 502 1 0.373 547 1 0 1345 1 -6.13 503 1 0.441 548 1 -0.001 1346 1 6.602 504 1 0.441 549 1 -0.005 1347 1 6.603 505 1 0.532 550 1 0.003 1348 1 -6.136 506 1 0.532 551 1 0.001 1349 1 -6.132 513 1 -164.2 567 1 -0.004 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |124|
  • 10. Analysis and Design of Transmission Tower 1350 1 -6.133 514 1 -164.2 568 1 0.002 1351 1 6.603 515 1 -188.2 569 1 0.004 1352 1 6.605 516 1 -188.2 570 1 -0.007 1353 1 6.605 517 1 -219.7 571 1 0.001 1354 1 6.607 518 1 -219.7 572 1 -0.001 1355 1 -6.134 525 1 -0.155 573 1 -0.001 1356 1 -6.133 526 1 -0.171 574 1 -0.005 III. DESIGN PARAMETERS Based on the wind speed map the entire country has been divided into six wind zones with max. wind speed of 55 m/sec. and min. wind speed of 33 m/sec. Basic wind speeds for the six wind zones are Wind Zone Basic Wind Speed (m/sec) 1 33 2 39 3 44 4 47 5 50 6 55 In case the line traverses across the border of wind zones, the higher wind speed may be considered. 3.1 Reference Wind Speed VR It is extreme value of wind speed over an average period of 10 minute duration and is to be calculated from basic wind speed 'vb' by the following relationship VR = Vb/K Where Ko is a factor to convert 3-second peak gust speed into average speed of wind during 10 minutes period at a level of 10 meters above ground. Ko is to be taken as 1.375. 3.2 Design Wind Speed Vd Reference wind speed obtained shall be modified to include the following effects to get the design wind speed: (i) Risk Coefficient K1 (ii) Terrain Roughness coefficient K2 It is expressed as follows:V = VR x K1 x K2 3.3 Risk Coefficient K1 Below Table gives the values of Risk Coefficient Kt for different wind zones for three Reliability Levels. Risk Coefficient K1 for Different Reliability Levels and Wind Zones Table No. 5.1 Reliability Level 1 Coefficient 3 K, 1(50 yr return period) 1.00 1.00 1.00 2(150 yr return period) 1.08 1.10 3 (300 yr return period) 1.17 1.22 wind 2 zones: 4 5 6 1.00 1.00 1.00 1.11 1.12 1.13 1.14 1.25 1.27 1.28 1.30 3.4 Terrain Roughness Coefficient K2 Below, gives the values of coefficient K2 of the three categories of terrain roughness corresponding to an average 10-minute wind speed. Terrain Roughness Coefficients K2 Terrain Category 1 2 3 Coefficient K2 1.08 1.00 0.85 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |125|
  • 11. Analysis and Design of Transmission Tower 3.5 Terrain Categories (a) Category 1 - Coastal areas, deserts and large stretches of water. (b) Category 2 - Normal cross-country lines with very few obstacles. (c) Category 3 - Urban built-up areas or forest areas. 3.6 Design Wind Pressure Pd The design wind pressure on towers, conductors and insulators shall be obtained by the following relationship:Pd = 0.6Vd2 where Pd = design wind pressure in N/m2 and Vd = Design wind speed in m/s. Design wind pressure Pd for all the three Reliability levels and pertaining to six wind zones and the three terrain categories have been worked out and given in Table below : Design Wind Pressure Pd, in N/m2 (Corresponding to wind velocity at 10 m height) Table No. 3.2 Reliabilit Terrain y Level Category 1 Wind pressure Pd for wind zones 2 3 4 5 6 1 563 717 818 925 1120 346 483 614 701 793 960 3 250 349 444 506 573 694 1 470 681 883 1030 1180 1460 2 403 584 757 879 1010 1250 3 291 422 547 635 732 901 1 552 838 1120 1320 1520 1890 2 473 718 960 1130 1300 1620 3 3 403 2 2 1 342 519 694 817 939 1170 3.7 Wind Loads (A) Wind Load on Tower In order to determine the wind load on tower, the tower is divided into different panels having a height 'h'. These panels should normally be taken between the intersections of the legs and bracings. For a lattice tower, the wind load Fwt in Newtons, for wind normal to a face of tower, on a panel height 'h' applied at the centre of gravity of the panel is :Fwt = Pd x Cdt x Ae x GT Pd = Design wind pressure in N/m2 Cdt = Drag Coefficient pertaining to wind blowing against any face of the tower. Values of C dt for the different solidity ratios are given in Table Ae = Total net surface area of the legs and bracings of the panel projected normally on face in m 2. (The projections of the bracing elements of the adjacent faces and of the plan-and-hip bracing bars may be neglected while determining the projected surface of a face). GT = Gust Response Factor, perpendicular to the ground roughness and depends on the height above ground. Values of GT for the three terrain categories are given in Table below, Drag Coefficient Cdt for Towers Table No. 3.3 Solidity Ratio Drag Coefficient, Cdt Upto 0.05 3.6 0.1 3.4 0.2 2.9 0.3 2.5 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |126|
  • 12. Analysis and Design of Transmission Tower 0.4 2.2 0.5 and above 2.0 Solidity ratio is equal to the effective area (projected area of all the individual elements) of a frame normal to the wind direction divided by the area enclosed by the boundary of the frame normal to the wind direction. Gust Response Factor for Towers (GT) and for Insulators (Gl) Table No. 3.4 Height above Values of GT and Gl for terrain Category 2 3 Upto 10 1.70 1.92 2.55 20 1.85 2.20 1.96 2.30 2.98 40 2.07 2.40 3.12 50 2.13 2.48 3.24 60 2.20 2.55 3.34 70 2.26 2.62 3.46 80 2.31 2.69 1 2.82 30 Ground m 3.58 (B) Wind Load on Conductor and Groundwire The load due to wind on each conductor and groundwire, Fwc in Newtons applied at supporting point normal to the line shall be determined by the following expression : Fwc = Pd. L. d. Gc. Cdc where: Pd = Design wind pressure in N/m2; L= Wind span, being sum of half the span on either side of supporting point, in metres.d = Diameter of conductor/groundwire, in metres. Gc = Gust Response Factor which takes into account the turbulance of the wind and the dynamic response of the Conductor. Values of Gc are already discussed for the three terrain categories and the average height of the conductor above the ground. Cdc = Drag coefficient which is 1.0 for conductor and 1.2 for Groundwire. (C) Wind Load on Insulator Strings Wind load on insulator strings 'Fwi' shall be determined from the attachment point to the centre line of the conductor in case of suspension tower and upto the end of clamp in case of tension tower, in the direction of the wind as follows : Fwi = 1.2. Pd. Ai. Gi Where Pd = Design Wind pressure in N/m2 Ai = 50 Per cent of the area of Insulator string projected on a plane parallel to the longitudinal axis of the string (1/2 x diameter x length). Gi = Gust Response Factor, depending on the ground roughness and height of insulator attachment above ground. Values of Gi for the three terrain categories. 3.8 Temperature To evolve design of tower, three temperatures i.e. Max. temperature, min. temperature and everyday temperature are very important. Tower height as well as sag and tension calculations of conductor and earthwire vary with the change in the above three temperatures. The temperature range varies for different parts of India under different seasonal conditions. The absolute max. and min. temperatures which may be expected in different localities in country are indicated on the maps of India respectively. The temperatures indicated in these maps are the air temperatures in shade. The max. conductor temperatures may be obtained after allowing increase in temperature due to solar radiation and heating | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |127|
  • 13. Analysis and Design of Transmission Tower effect due to current etc. over the absolute max. temperature given below. After giving due thought to several aspects such as flow of excess power in emergency during summer time etc. the following three designs temperatures have been fixed :(a) Max. temperature of ACSR conductor = 75 deg C (b) Max. temperature of AAAC conductor = 85 deg C (c) Max. temperature of earthwire = 53 deg C (d) Min. temperature (ice-free zone) = - 5 deg C to + 10 deg C (depends on location of the trans, line however 0°C widely used in the country) (e) Everyday Temperature 32°C (for most parts of the country). For region with colder climates (-5 deg C or below) the respective Utility will decide the everyday temperature. 3.9 Lightning Consideration for Tower Design As the overhead transmission lines pass through open country, these are subjected to the effects of lightning. The faults initiated by lightning can be of the following three types:(i) Back flash over: When lightning strikes on a tower or on the earthwire near the tower which raises the tower potential to a level resulting in a discharge across the insulator string. (ii) Midspan flash over: When lightning strikes on earth wire raising local potential of the earth wire such that a breakdown in the air gap between earthwire and phase conductor results. (iii) Shielding failure: When lightning strikes on the phase conductor directly resulting in a flashover across the insulator string. 3.10 Seismic Consideration The transmission line tower is a pin-jointed light structure comparatively flexible and free to vibrate and max. wind pressure is the chief criterion for the design. Concurrence of earthquake and max. wind condition is unlikely to take place and further siesmic stresses are considerably diminished by the flexibility and freedom for vibration of the structure. This assumption is also in line with the recommendation given in cl. no. 3.2 (b) of IS: 1893-1984. Seismic considerations, therefore, for tower design are ignored and have not been discussed in this paper. 3.11 New Concepts in Transmission Line Design The new concepts in transmission line design philosophy include the following major changes in the design method :(i) Design based on limit load concept; (ii) Use of probablistic method of design; (iii) Use of Reliability levels in transmission lines design; (iv) Use of Co-ordination in strength of line components; (v) Use of six basic wind speeds converted to 10-minutes average speeds corresponding to 10-meter height over mean retarding surface as the basis for wind loads on transmission lines instead of three wind zones corresponding to 30 metre height over mean retarding surface in use earlier; (vi) Consideration of the effects of terrain category and topography of transmission line corridors in the design wind speeds. IV. DESIGN OF TRANSMISSION LINE TOWER 4.1 Design of leg member NC 32°C & 100% wind GW (2018+745) * 53.95 = 149064 TC (2*7760+2777)*46.5 = 850811 MC (2*7760+3030)*41 = 760550 BC (2*7760+2972)*35.5 = 656466 TC1 (3954*2+3308)*28.5 = 319656 MC1 (2*3954+2662)*24= 253680 BC1 (2*3954+2739)*19.5= 207617 M = 3198X103 Kg- m Max. Stress = M/2wcosø = 3198bX103/2*5.4*0.9982 = 296 X 103 Vertical load max = 256 +2512*6+1268*6 4 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |128|
  • 14. Analysis and Design of Transmission Tower = 5734 Vertical load min = 119+1871*6+956*6 4 = 4270 Self wt of tower = 10000/4 = 2500 approx. Compression = 305 X 103 Tension = 290 X 103 Use ISA 100X100X8 Double angle back to back section L= 2340/0.999 = 2342.342 l/r = 234.23/3.07 = 76.296 yield stress of mild steel = 2550 Kg/cm2 from curve no. 1 Fc = 2503 ultimate compressive stress = 2503*30.78 = 77204 < 305 X 103 Use ISA 200X200X25 Double angle back to back section l/r = 38.5 = 39 ultimate compressive stress = 2427*183.30 = 445 X 103 > 305 X 103 S.M. = 1.46 K= 5A1 5A1+ A2 = 5*200*25 5*200*25+200*25 = 0.833 Net area for tension = (200*25+0.833*200*25)*2 = 183.30 ultimate tensile stress = 2550*183.30 = 467 X 103 > 305 X 103 S.M. = 1.233 Use 20mm dia bolts 6Nos. Ultimate shearing strength (single shear) = 59586 kg Ultimate bearing strength (single shear) = 98018 kg Ultimate shearing strength (double shear) = 119X10 kg 4.2 Design of bracings ∑Fb for transverse face bracing GW (2018+745) * 0.2 = 2763 TC (2*7760+2777)*3 = 54891 MC (2*7760+3030)*3 = 55650 BC (2*7760+2972)*3 = 55476 TC1 (3954*2+3308)*3.59 = 40265 MC1 (2*3954+2662)*3.97= 41963 BC1 (2* 3954+2739)* 4.52 = 47912 ∑Fb = 355 X 103 Stress = ∑Fb / 4wcosø = 355 X103 / 4*5.4*0.9982 = 16 X 103 (C&T) L= 2320 Use ISA 90 X 90 X 12 Double angle back to back section l/r = 232/2.270 = 85.6 ultimate compressive stress = 1726*28.74 = 48 X103 > 16 X 103 S.M. = 3 K = 5A1 5A1+ A2 = 5*90*12 5*90*12+90*12 = 0.833 Net area for tension = (90*12+0.833*90*12)*2 = 40 cm2 ultimate tensile stress = 2550* 40 = 102 X 103 > 16 X 103 S.M. = 6.37 Use 20mm dia bolts 4Nos. | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |129|
  • 15. Analysis and Design of Transmission Tower Ultimate shearing strength (single shear) = 39724 Ultimate bearing strength (single shear) =65345 Ultimate shearing strength (double shear) = 79333 4.3 Design of other diagonals Stress = 16 X103 (C&T) L= 2390 Use ISA 65X65X8 single angle section l/r = 239/1.25 = 191.2 Ultimate compressive stress = 1387*9.76 = 13.53x 103 < 16 X 103 Use ISA 100 X 100 X 8 single angle section l/r = 239/3.07 = 77.85 K= 3A1 3A1+ A2 = 3*100*8 3*100*8+100*8 = 0.75 Net area for tension = (100*8+0.75 *100 *8) = 14 ultimate tensile stress = 2550*14 = 35.7 X 103 > 16 X 103 S.M. = 2.18 Use 20mm dia bolts 6Nos. Ultimate shearing strength (single shear) = 39724 Ultimate bearing strength (single shear) = 65345 Ultimate shearing strength (double shear) = 79333 4.4 Design of cross arm a) Upper member:Length = √(1.3752+4.842) = 5.032 St = 1406*5.032 2*4.84 = ± 731 Sv = 3214*5.032 2*1.375 = 5881 Sl = 4109*5.032 2*3 = ± 3446 Compression = 10056 Tension = 4177 L = 5.032/3 = 1.677 l/r = 167.7 / 3.07 = 54.625 ultimate compressive stress = 1970*28.74 = 55 X103 >10 X103 S.M. = 3.43 K= 5A1 5A1+ A2 = 5*100*8 5*100*8+100*8 = 0.833 Net area for tension = (100*8 + 0.833*100 *8)*2 = 29.32 Ultimate tensile stress = 2550*29.32 = 75 X103 > 4.1X103 b) Lower member :Length = √(1.3752+4.842+32 = 5.858 Sv = 3984*5.858 2*1.375 = 8487 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |130|
  • 16. Analysis and Design of Transmission Tower l/r = 585.8 / 3.07 = 191 Ultimate tensile stress = 2550*30.7 = 78 X103 > 4.1 X103 Use 20mm dia bolts 6Nos. Ultimate shearing strength (single shear) = 39724 Ultimate bearing strength (single shear) =65345 Ultimate shearing strength (double shear) = 79333 CONCLUSION: Use ISA 200X200X 25 Double angle back to back section for leg member Use ISA 90X90X 12 Double angle back to back section for bracings and cross arm Use ISA 100x100X 8 Single angle section for other diagonals. 4.5 RESULT :Compression and Tensile force acting on the tower and obtained from STAAD Pro-V8i are as, Table No. 6.1 LEG MEMBER Compres s-ion kg BRACINGS Beam L/C Compression kg Tension Kg Beam L/C Compression kg Tension Kg 2.34E+05 6 1 14841.721 -14841.721 123 1 -0.829 0.453 3.12E+05 10 1 15860.281 -19851.965 124 1 0.418 0.437 3.59E+05 14 1 16901.445 -22902.618 125 1 -1.113 0.428 3.24E+05 33 1 -54.179 -21272.222 126 1 0.136 0.435 2.90E+05 37 1 -59.751 -19508.161 127 1 0.705 0.441 2.55E+05 63 1 -34421.587 -17593.517 128 1 -0.798 0.448 2.39E+05 64 1 -39525.147 -16374.135 129 1 0.36 0.452 3.07E+05 65 1 -46225.431 -20052.837 130 1 -1.545 0.438 2.75E+05 69 1 130.627 -18332.961 131 1 0.235 0.444 2.46E+05 2.43E+05 70 1 154.341 -16457.506 132 1 0.673 0.451 1 2.10E+05 3.26E+05 71 1 185.709 -21182.74 133 1 -0.47 0.434 197 1 1.67E+05 2.94E+05 87 1 -34421.643 -19307.288 134 1 0.092 0.441 213 1 2.46E+05 2.90E+05 88 1 -34421.805 -19223.915 135 1 -0.961 0.441 214 1 2.46E+05 2.92E+05 89 1 -39524.799 -19396.77 136 1 0.37 0.441 215 1 2.10E+05 2.87E+05 90 1 -39525.847 -19313.396 137 1 0.642 0.442 216 1 2.10E+05 2.85E+05 91 1 -46222.823 -19424.788 153 1 -0.506 0.442 217 1 1.67E+05 1.44E+05 92 1 -46224.895 -8827.504 154 1 0.313 0.471 218 1 1.67E+05 2.10E+05 99 1 130.386 -13042.086 155 1 0.188 0.458 333 1 2.36E+05 2.50E+05 100 1 130.659 -15611.98 156 1 -0.847 0.45 334 1 2.01E+05 2.21E+05 101 1 154.67 -14324.424 157 1 0.136 0.455 335 1 1.59E+05 1.92E+05 102 1 154.66 -12927.625 158 1 -0.172 0.461 351 1 2.36E+05 1.64E+05 103 1 186.274 -11407.839 159 1 -0.015 0.466 352 1 2.36E+05 1.49E+05 104 1 186.303 -10304.371 160 1 -0.511 0.469 353 1 2.01E+05 2.06E+05 111 1 14841.632 -13220.955 161 1 0.235 0.458 354 1 2.01E+05 1.80E+05 112 1 15860.208 -11840.116 162 1 -0.188 0.463 355 1 1.59E+05 1.53E+05 113 1 16901.384 -10357.731 163 1 -0.213 0.469 356 1 1.59E+05 2.23E+05 117 1 -54.179 -14243.94 164 1 0.021 0.455 Beam L/C 57 1 58 1 59 1 75 1 76 1 77 1 78 1 79 1 80 1 2.34E+05 1.98E+05 1.55E+05 2.34E+05 2.34E+05 1.98E+05 1.98E+05 1.55E+05 1.55E+05 195 1 196 Tension Kg OTHER DIAGONALS | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |131|
  • 17. Analysis and Design of Transmission Tower 471 1 472 1 473 1 489 1 490 1 491 1 492 1 493 1 494 1 597 1 598 1 599 1 600 1 605 1 606 1 607 1 608 1 609 2.24E+05 1.89E+05 1.48E+05 2.24E+05 2.24E+05 1.89E+05 1.89E+05 1.48E+05 1.48E+05 4.55E+04 5.07E+04 58371.33 4 1.96E+05 118 1 -59.751 -12748.756 165 1 -0.747 0.46 1.92E+05 183 1 54.877 -12695.395 166 1 0.37 0.461 1.94E+05 184 1 60.565 -12829.239 167 1 -0.188 0.46 1.90E+05 185 1 -5686.867 -12775.879 261 1 -0.398 0.461 1.88E+05 189 1 -13992.334 -12874.265 262 1 0.207 0.462 5.23E+02 190 1 -14923.574 12.473 263 1 -0.253 0.499 4.83E+03 191 1 -16265.538 896.249 264 1 0.05 0.499 3.44E+04 201 1 -130.396 42.547 265 1 0.188 0.493 4.05E+04 202 1 -154.044 589.199 266 1 -0.749 0.492 6.72E+04 203 1 -185.83 -325.072 267 1 0.522 0.487 7.05E+04 207 1 34422.623 244.492 268 1 -0.588 0.487 9.44E+04 208 1 39527.652 -744.483 269 1 -0.056 0.482 9.91E+04 209 1 46225.82 -703.693 270 1 0.188 0.481 1.08E+05 225 1 -130.33 -1189.658 271 1 -0.544 0.48 1.10E+05 226 1 -130.151 -1012.746 272 1 0.309 0.479 1.17E+05 227 1 -154.52 -1505.023 273 1 0.12 0.478 1.18E+05 228 1 -154.033 -1341.662 274 1 -0.204 0.478 1 5.38E+04 3.50E+04 2.38E+04 3.94E+04 2.75E+04 45677.37 1 1.24E+05 229 1 -186.139 -1838.798 275 1 0.188 0.476 610 1 32185.73 1.98E+05 230 1 -185.827 -15860.281 291 1 -0.924 -0.418 611 1 4.05E+04 2.64E+05 237 1 34422.082 -21371.774 292 1 0.295 -0.441 612 1 3.02E+05 238 1 34422.309 -24727.628 293 1 0.705 -0.455 681 1 2.71E+05 239 1 39526.762 -22934.119 294 1 -0.474 -0.449 682 1 2.96E+04 1.56E+04 1.79E+04 2.40E+05 240 1 39526.351 -20993.571 295 1 0.05 -0.442 683 1 2.12E+05 241 1 46223.461 -18887.38 296 1 -1.944 -0.435 684 1 1.98E+05 242 1 46225.393 -17546.002 297 1 0.319 -0.429 689 1 2.57E+05 249 1 54.877 -21592.743 298 1 -0.028 -0.443 690 1 2.29E+05 250 1 60.565 -19700.799 299 1 -0.056 -0.436 691 1 2.02E+05 251 1 -5686.867 -17637.717 300 1 0.297 -0.429 692 1 2.35E+04 21053.53 5 1.06E+04 5.04E+03 1.28E+04 6.14E+03 2.74E+05 255 1 -13992.246 -22835.685 301 1 -0.825 -0.448 693 1 1.60E+04 2.47E+05 256 1 -14923.499 -20772.602 302 1 0.239 -0.44 694 1 2.43E+05 257 1 -16265.479 -20680.889 303 1 0.334 -0.44 695 1 8548.971 13216.78 3 2.44E+05 321 1 -13345.315 -20871.037 304 1 -0.204 -0.441 696 1 2.40E+05 322 1 -14213.476 -20779.323 305 1 0.266 -0.441 761 1 2.36E+05 323 1 -15488.474 -20901.858 399 1 -1.554 -0.443 762 1 8.01E+03 2.58E+03 3.51E+03 1.22E+05 327 1 -54.355 -9542.891 400 1 0.298 -0.393 763 1 3.60E+03 1.78E+05 328 1 -59.594 -14179.118 401 1 -0.488 -0.412 764 1 5.11E+03 2.11E+05 329 1 -5820.379 -17006.116 402 1 0.052 -0.423 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |132|
  • 18. Analysis and Design of Transmission Tower 829 1 1.84E+05 339 1 32880.296 -15589.747 403 1 0.705 -0.419 1.59E+05 340 1 37701.356 -14053.207 404 1 -0.899 -0.414 1 1.59E+05 1.49E+05 1.41E+05 830 1 831 1.35E+05 341 1 44024.688 -12381.374 405 1 0.32 -0.408 832 1 1.51E+05 1.23E+05 345 1 130.405 -11167.509 406 1 -0.063 -0.403 833 1 1.73E+05 346 1 154.517 -14375.882 407 1 -0.05 -0.414 834 1 1.49E+05 347 1 186.313 -12856.898 408 1 0.673 -0.408 835 1 1.54E+05 1.33E+05 1.24E+05 1.27E+05 363 1 32879.77 -11226.208 409 1 -0.817 -0.402 836 1 1.87E+05 364 1 32879.033 -15501.213 410 1 0.235 -0.418 873 1 1.45E+05 1.08E+05 1.65E+05 365 1 37700.494 -13856.443 411 1 0.304 -0.412 874 1 1.37E+05 1.61E+05 366 1 37701.614 -13797.744 412 1 -0.192 -0.412 875 1 1.62E+05 367 1 44022.448 -13944.979 413 1 0.642 -0.413 876 1 1.58E+05 368 1 44024.287 -13886.278 429 1 -0.396 -0.413 885 1 1.45E+05 1.17E+05 1.08E+05 1.55E+05 375 1 130.473 -13994.508 430 1 0.205 -0.414 886 1 1.30E+05 5.76E+02 376 1 130.652 13.566 431 1 0.188 -0.355 887 1 4.95E+03 377 1 154.046 985.761 432 1 -0.254 -0.348 888 102 2 102 3 102 4 1 3.20E+04 378 1 154.534 46.651 433 1 0.052 -0.349 1 1.20E+05 9.90E+04 5.55E+04 3.74E+04 379 1 186.008 647.994 434 1 -0.739 -0.344 1 7.33E+04 6.12E+04 380 1 186.328 -357.743 435 1 0.513 -0.346 1 6.39E+04 387 1 -13345.404 268.804 436 1 -0.593 -0.341 8.43E+04 388 1 -14213.549 -819.112 437 1 -0.05 -0.344 8.75E+04 389 1 -15488.535 -774.241 438 1 -0.188 -0.343 1 7.89E+04 61205.53 4 68855.22 3 8.72E+04 9.44E+04 393 1 -54.355 -1308.823 439 1 -0.536 -0.345 1 9.26E+04 9.54E+04 394 1 -59.594 -1114.211 440 1 0.302 -0.343 1 1.05E+05 1.01E+05 395 1 -5820.379 -1655.738 441 1 0.103 -0.345 1 9.97E+04 1.00E+05 459 1 55.06 -1476.032 442 1 -0.192 -0.344 1 1.04E+05 460 1 60.507 -2022.903 443 1 -0.188 -0.347 1.55E+05 465 1 14195.828 -16901.445 537 1 -0.508 0.737 1 1.13E+05 75980.94 5 9.57E+04 2.07E+05 466 1 15149.086 -24335.337 538 1 0.316 0.847 1 1.54E+03 2.35E+05 467 1 16099.075 -28262.859 539 1 -0.847 0.914 1 8.58E+01 2.07E+05 477 1 -130.19 -25499.538 540 1 0.134 0.876 1 1.60E+03 1.82E+05 478 1 -154.237 -22723.928 541 1 0.188 0.836 1 7.79E+02 1.60E+05 479 1 -186.385 -19676.647 542 1 -0.366 0.793 1 -3364.292 1.50E+05 483 1 -32878.314 -18270.415 543 1 0.166 0.767 1 -1671.922 1.98E+05 484 1 -37700.855 -24093.307 544 1 -0.98 0.85 1 3.51E+03 1.74E+05 485 1 -44023.549 -21464.388 545 1 0.229 0.811 1 1.82E+03 1.54E+05 501 1 -130.432 -18796.407 546 1 0.188 0.769 102 5 103 0 103 1 103 2 103 3 103 4 103 5 103 6 103 7 130 4 130 5 130 6 130 7 130 8 130 9 131 0 131 1 1 1 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |133|
  • 19. Analysis and Design of Transmission Tower 1 132 8 134 5 134 6 134 7 134 8 134 9 135 0 135 1 135 2 135 3 135 4 135 5 135 6 1 1.67E+03 1.92E+03 1 2.07E+03 1.88E+05 504 1 -154.159 -22439.97 549 1 -0.729 0.831 1 1.87E+05 505 1 -185.824 -22831.554 550 1 0.357 0.834 1.83E+05 506 1 -185.802 -22305.566 551 1 0.188 0.832 1.78E+05 513 1 -32878.379 -22197.94 567 1 -0.831 0.833 1 2072.773 1.93E+03 1.92E+03 1.92E+03 9.52E+04 514 1 -32878.535 -10465.731 568 1 0.416 0.611 1 2074.123 1.40E+05 515 1 -37699.825 -16702.273 569 1 0.705 0.704 1 2076.314 1.64E+05 516 1 -37701.11 -20004.543 570 1 -1.099 0.76 1 2074.688 1.40E+05 517 1 -44022.345 -17794.725 571 1 0.134 0.73 1 2076.878 1.92E+03 1.92E+03 1.19E+05 518 1 -44023.786 -15575.305 572 1 -0.468 0.698 9.98E+04 525 1 55.06 -13011.355 573 1 0.049 0.663 9.16E+04 526 1 60.507 -11735.359 574 1 -0.659 0.639 1 1 1 1 1 2.12E+05 502 1 -130.158 -25633.943 547 1 -0.22 0.875 1.91E+05 503 1 -154.311 -22965.958 548 1 0.028 0.833 4.6 Foundation Details :FOUNDATION LOADINGS Kg Compression = 2.77 * 105 Tension = 2.77 * 105 Transverse = 23860.5 Longitudinal = 10594.9 STRUCTURE DETAIL Width (Trans.) X Width (Long.) 6M X 6M Slope (Trans.) X Slope (Long.) 2.419509 ° X 2.419509 ° True Length Factor Transverse 1.00089 Longitudinal 1.00089 FOUNDATION PROFILE Depth of Foundation = 2M Transverse Width = 1.8 M Longitudinal Width = 1.8M Height of concrete block = 1.5M Depth of Anchor/Grout bar = 1.2M Height of chimney = 0.5M Chimney Width = 0.75M Muffing Height = 0.35M SOIL DETAIL Type of Soil ----------- HARD ROCK Weight of Rock = 1600 Kg/cu.m U.B.C = 125000 Kg/Sq.m Frictional resistance between rock and concrete = 4 kg/Sq.cm Frictional resistance between rock and grout (As per CBIP manual pg. no. 267 ) Weight of concrete Fe = 415 N/mm2 Fck = 2 N/mm2 = 2 kg/Sq.cm. = 2300 Kg/Sq.m | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |134|
  • 20. Analysis and Design of Transmission Tower FOUNDATION DESIGN CALCULATION Volume of concrete in M³ Muffing = 0.197 M3 Chimney = 0.281 M3 Concrete block = 4.860 M3 Total = 5.338 M3 Over load due to Concrete in Kg Muffing = 452.81 Chimney = 196.88 Concrete block = 3402.00 Total = 4051.69 Kg Total thrust on foundation = 277000 = 281051.69 CHECK OF FOUNDATION IN BEARING Ultimate strength of rock in bearing = 1.8 ² = 405000 Kg = 405000 > 281051 F.O.S = 1.44 + 4051.69 Kg x 125000 CHECK OF FOUNDATION IN UPLIFT Concrete block Net uplift = 277000 4051.69 = 272948 Kg Ultimate frictional strength between rock and concrete = 180 X 150 X 4 X 4 = 432000 Kg Uplift resisted by 4 NOS. 20 ɸ = (No. of bar X pi(π) X Dia. of bar X Depth of anchor bar X Bond between rock & Grout ) = 4 X 3.14 X 2 X 120 X 2 = 6028.80 …….. (I) = Bond between rock anchor steel and grout = π X 2 X 120 X 12 X 4 = 36191.14 > 6028.80 ………. (II) Total resistance against uplift = 438028.80 > FOS = 1.623 = 432000 + 6028.80 272948 (Min. of ((I) & (II)) ANCHOR (TOR) BARS ASSUMED CHECK AGAINST UPROOTING OF STUB SECTION OF STUB JL 200X200X16 Cover = 10 Cm Design Uplift = 277000 Kg Cleats Provided = 6 NOS OF 110X110X10 Bolts = 24 Nos of 20 mm dia. Ultimate resistance of Stub in Bond = US = [D x{X x 2.0+ (X-Ts) x 2.0}-Np x {X+(X-Ts)} x k] x S Where , X = Flange width of Stub = 20 cm D = Depth of Stub in slab ( Concrete Block) = 140 cm S = Ultimate permissible bond stress between stub and concrete = 12 kg/cm²……. manual) Ts = Thickness of stub section = 1.6 cm Np = No of cleat pair (Pair consists of outer & inner cleats) = 6 Nos. k = Flange width of cleat section = 11 cm Us = (140 X (20 X 2.0 + (20 - 1.6 ) X 2.0) - 6 X (20+ (20 - 1.6 )) X 11) X 12 = 98611 kgs | IJMER | ISSN: 2249–6645 | www.ijmer.com Page No.267 (CBIP | Vol. 4 | Iss. 1 | Jan. 2014 |135|
  • 21. Analysis and Design of Transmission Tower Load resisted by cleat in bearing :Least resistance offered by cleats in bearing / bolt :x (k-Ct) Where, b = Ultimate bearing pressure in concrete = 91.75 cm Lo = Length of outer cleat = 40 cm Li = Length of inner cleat = 25 cm Ct = Thickness of cleat section = 1.0 cm Uc = 91.75 X ( 40 + 25) X 6 X (11 - 1) = 357825 kg…………. (I) Resistance against uplift : = 98611.2 + 357825 456436 > 277000 FOS = 1.648 Uc = b x (Lo+Li) x Np NOTE: 1 Nominal Reinforcement provide. 2 Stub to be cut, holes to be drilled and cold zinc rich paint/galvanising to be applied at site. 3 Grout holes to be 20 mm bigger than dia of grout bar. 4 Cement sand mix 1:1 Ratio to be used for grouting through grouting pump. 5 Entire concrete block (slab) should be embedded in hard rock irrespective of level of hard rock encountered. 4.6.1 Details of foundation drawing is given | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |136|
  • 22. Analysis and Design of Transmission Tower V. CONCLUSION Narrow based steel lattice transmission tower structure plays a vital role in its performance especially while considering eccentric loading conditions for high altitude as compared to other normal tower. Narrow based steel lattice transmission tower considered in this paper can safely withstand the design wind load and actually load acting on tower. The bottom tier members have more role in performance of the tower in taking axial forces and the members supporting the cables are likely to have localized role. The vertical members are more prominent in taking the loads of the tower than the horizontal and diagonal members, the members supporting the cables at higher elevations are likely to have larger influence on the behavior of the tower structure. The effect of twisting moment of the intact structure is not significant. The Geometry parameters of the tower can efficiently be treated as design Variables and considerable weight reduction can often be achieved as a result of geometry changes.The tower with angle section and X-bracing has the greater reduction in weight after optimization . Tube section is not economic to use in this type of transmission tower. Total weight of tower considering weight of nut bolts, anchor bolts, hardware etc works out to 30 to 35 Tonne. Scope of Present Work:a) Continuous demand due to increasing population in all sectors viz. residential, commercial and industrial leads to requirement of efficient, consistent and adequate amount of electric power supply which can only fulfilled by using the Conventional Guyed Transmission Towers. b) It can be substituted between the transmission line of wide based tower where narrow width is required for certain specified distance. c) Effective static loading on transmission line structure, conductor and ground wire can be replaced with the actual dynamic loading and the results can be compared. d) Attempt in changing the shape of cross arm can lead to wonderful results. e) Rapid urbanization and increasing demand for electric, availability of land leads to involve use of tubular shape pole structure. f) lso restricted area (due to non-availability of land), more supply of electric energy with available resources and for continuous supply without any interruption in the transmission line, will demand the use of high altitude narrow based steel lattice transmission tower REFERENCES Journal [1] [2] Y. M. Ghugal, U. S. Salunkhe “Analysis and Design of Three and Four Legged 400KV Steel Transmission Line Towers: Comparative Study ” International Journal of Earth Sciences and Engineering 691 ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp 691-694 V. Lakshmi1, A. Rajagopala Rao “ Effect Of Medium Wind Intensity On 21M 132kV Transmission Tower” ISSN: 2250–3676 Volume-2, Issue-4, 820 – 824 | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |137|
  • 23. Analysis and Design of Transmission Tower [3] [4] [5] [6] [7] [8] [9] [10] [11] M.Selvaraj, S.M.Kulkarni, R.Ramesh Babu “Behavioral Analysis of built up transmission line tower from FRP pultruded sections” ISSN 2250-2459, Volume 2, Issue 9, september 2012 S.Christian Johnson 1 G.S.Thirugnanam “Experimental study on corrosion of transmission line tower foundation and its rehabilitation” International Journal Of Civil And Structural Engineering ISSN 0976 – 4399 Volume 1, No 1, 2010 F. Albermani, M. Mahendran and S. Kitipornchai “Upgrading of Transmission Towers Using a Diaphragm Bracing System” International Journal Of Civil And Structural Engineering Volume2, No2, 2008 N.PrasadRao, G.M.SamuelKnight, S.J.Mohan, N. Lakshmanan “Studies on failure of transmission line towers in testing” G.Visweswara Rao “ Optimum Designs For Transmission Line Towers” Computer & Structures vol.57.No.1.pp.81-92, 1995 Indian Standards,”Use of structural steel in overhead transmission line tower”,IS 802(part 1):1967, Bureau of Indian Standards , New Delhi. Indian Standards,”General construction in steel”IS 800:2007, Bureau of Indian Standards , New Delhi Indian Standards,”Aluminium conductors for overhead transmission purposes”IS 398(part II):1976, Bureau of Indian Standards , New Delhi. Indian Standards,”Galvanised stay strand (second revision)”IS 2141:1779, Bureau of Indian Standards New Delhi. | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 1 | Jan. 2014 |138|